The present invention relates to a means for recording droplet impacts. More particularly, this invention concerns itself with a means for measuring and detecting the production of liquid droplets formed from unreacted rocket motor fuel.
With the recent advent of missile and satellite systems, considerable interest has been generated in the development of testing means for evaluating the operational efficiency of rocket motors. These motors, especially those of the smaller type, are normally operated in space in a pulsed mode; during this operation, a certain amount of fuel and/or oxidizer is expelled without reaction. This phenomenon is most pronounced at the beginning or end of operation of the motor, due to irregularities in the rates of opening of the fuel and oxidizer supply valves and the low temperatures and pressures in the combustion chamber.
The unreacted material which is expelled from a rocket motor is of interest because it indicates imcomplete reaction, it may be highly corrosive, and because it may interfere in various ways with any optical systems used on the space vehicle. These optical systems may have a variety of functions, including scientific observations, spacecraft attitude control, and tracking, guidance, and target discrimination. As the optical systems used on spacecraft become more sensitive and capable of more refined discrimination, the potential interference due to contamination becomes more serious.
In addition to optical systems, engine-produced contaminants can interfere with other important systems on the spacecraft, such as thermal control coatings and solar cells. Finally, certain reaction products deposited on surfaces have the potential of being more explosive than dynamite and are shock sensitive.
For engine diagnosis and testing, it is desirable to be able to observe the quantity and size of particles of unreacted material, and to be able to state at which part of the rocket motor pulse the material was expelled. However, since these materials are normally volatile, collection is very difficult. In addition, any droplets which are formed may be very small. The customary method of visual analysis and evaluation of the droplet characteristics has not proven successful. The effectiveness of such a method depends entirely on the experience, judgment and ability of the individuals conducting the test analysis, and the results obtained vary accordingly and are lacking in sufficient reliability. However, with the present invention, the problems referred to above have been overcome since fairly accurate test results can now be obtained in a reproducible manner not heretofore achieved.
As far as is known, no techniques are presently available which allow measurement of number, size, and time of production of droplets from rocket motors which operate within the space environment.